I want to talk about one of the most powerful agents of change of the last 100 years. Put aside your expectations. This force was an uncharismatic thin man with glasses and a fondness for tinned tomato soup who was not part of government and concentrated his energies in some of the poorest areas of the East End of London.

There he was to be found, often as not, chatting to people at bus stops or sitting talking to families in their homes over cups of tea. On one occasion he became so engrossed in a conversation with someone he had met grieving in a graveyard that he forgot about his family's Christmas dinner. On another occasion he tried to get a grant to live as a hobo for a few months.

What his life tells us about the process of change is profound, but little understood.

Most of the people involved in politics and government think that the changes which really matter comes from political parties which set agendas, win votes, pass legislation. The history books and the evening news present a world governed by the decisions of great and powerful men (usually), fighting bitter battles in elections and cutting deals in smoke filled rooms (well the smoke has gone).

In these programmes I've been looking at perception and reality in politics and government, at who can be trusted and at whether power has really drained away for government. In this programme I'm going to look deeper at how change happens. I'll be asking how much politicians lead - and how much are they really followers. And are the most successful governments the ones that do things to us or the ones that make it possible for people to do more for themselves?

Looking back over the last century or so few governments have really changed the weather and left a lasting legacy. The ones that did include Asquith's Liberal administration of 1906 which introduced the embryonic welfare state gave powers to trade unions and cut back the powers of the aristocracy.

Clement Attlee's Labour administration of 1945 also made the grade, with the creation of the NHS, a wave of nationalizations, and the decolonization of India, as did Margaret Thatcher's Conservative government after 1979 with its programme of trade union legislation, privatizations and deregulations.

Each came to power helped by a hunger for change and a powerful wave of intellectual ideas. Each was willing to fight very bitter battles to get its way.

One of the things that made them strong was their values. President Mitterrand was once asked by his adviser Jacques Attali to define the most important quality in a leader and answered: 'indifference'. He enjoyed being called the Florentine, a reference to Machiavelli. But these governments by contrast were rarely indifferent. They cared about their beliefs and couldn't countenance sacrificing them.

And each stands out from the larger number of administrations which were content just to be in office: responding to the pressure of events, tinkering and fiddling or simply taking the view that if things weren't broken there was no need to fix them.

The jury is still out on whether the Blair government will join the list of Britain's truly transformative administrations. In 1997 although there was an appetite for change there wasn't quite the same sense of tectonic plates shifting as in 79 or 45. Part of Labour's promise was that it wouldn't change too much, and ever since 1997 it's been trying to strike a difficult balance between radicalism and continuity. In any case verdicts are very difficult from close up. It's worth remembering for example that in 1951 many commentators saw the Attlee government as a great disappointment.

But my guess is that the ultimate verdict will depend not only on whether new Labour's laws and ideas last, but also on whether it's seen to have crystallised something profound changing amongst us, the people, in the way that Margaret Thatcher's government seemed to embody a much broader tide of individualism.

To illustrate what I mean let's take another look at the man with the tomato-soup in east London. If you ask historians which individual did most to shape Britain's institutions and policies over the last 60 years many would give him a place alongside the more obvious candidates like Clement Attlee, Roy Jenkins and Norman Tebbit.

His name was Michael Young and he started his career very much as an insider - in fact he wrote Labour's 1945 manifesto, probably the purest example of a radical political programme that changed Britain.

But Michael Young then took a very different route to most politicians and in the mid-50s moved out to the east end where he set up a small institute.

His aim was to change the world for the better, but with very different tools: working more from the bottom up than from the top down. Much of what he did started with conversations - talking to people, doing ethnographic studies of families and communities, listening to where people's aspirations were being blocked.

Some of these sparked off new ideas and some of those ideas led him to create new organisations. So for example his experience of the bad deal that British consumers got from big companies led him to set up Which? and the Consumers Association, first as a one off magazine.

Talking to the people of Bethnal Green and realising how few ever imagined that university might be relevant to them or their children, led him to the idea of an Open University at which people could do courses at any time of their lives - and there are now several dozen around the world.

Conversations with people in hospitals led him to be profoundly sceptical of the excessive deference given to doctors - and so he set up a healthline that could give advice - the precursor to NHS Direct - and a College of health to put patients in the driving seat.

Alongside these he set up an organisation to represent grandparents, another to help with babynaming, a third to train new generations of social entrepreneurs - some 60 organisations in total. Along the way he also wrote extensively: on meritocracy, a word he coined; on how as society ages we would move away from the assumption that your chronological age determines what you're allowed to do; and on how we might organise death and dying in more humane ways.

In all of this his greatest interest was in ideas that would give people more power over their own lives and more ways to help each other. His trick was to look for small changes that could have potentially big leverage'. Having found them as one of his collaborators put it, he went on to struggle with 'sheer persistence, a kind of benign ruthlessness even, clutching onto an idea beyond the bitter end, always taking 'no' as a question.'

And although Whitehall and Westminster were often baffled by his ideas at first within 10 or 20 years they had often become mainstream, with many others claiming credit (Michael young understood very well American President Harry Truman's comment that 'Its amazing what you can achieve if you don't care who gets the credit'.)

His continuing significance, three years after his death at the age of 86, can be gauged by the number of items in this years Labour manifesto which can be directly traced to his influence - like extended schools, proposals for giving new powers to neighbourhoods, legislation against age discrimination, or the strong push for consumer power and choice in public services.

His was a quieter approach to change, and certainly took longer. The OU took 13 years from conception to giving birth to courses and students. Many of his ideas are still ahead of their times. But viewed in the long run this approach - spotting needs, setting things up small, and then seeing them grow by attraction and emulation, is as powerful as the more obvious changes that come from laws and spending.

So we can see two very different ways of thinking about change. In one governments impose change on a passive society through laws and policies. The job of government is to lead and indeed if there isn't much resistance then that's probably a sign that government isn't trying hard enough.

In the other change grows more from the bottom up; by choice and voluntary action, by attraction rather than imposition. In this view the most far-reaching ideas and changes come from outside, from social movements and movements of ideas and Governments are more often vehicles than initiators. They may play a critical role in embedding changes - like debt cancellation for Africa, or regulations to arrest climate change. But there are very few things that they initiate.

Government in other words can be a great orchestrator - but it doesn't make up the tunes, or play many of the instruments.

These two approaches to change aren't mutually exclusive.

Take public health - how much is government leading when it talks about smoking bans, and how much is it responding to decades of public action and a culture that has turned decisively against smoking? Or take childcare - how much is government's commitment to extend childcare an act of leadership, and how much is it a belated response to profoundly changed working lives and decades of social change in nurseries, childminding, much of it led by the voluntary sector?

Even Labour's programme in 1945 can be seen through both lenses - much of it came from beyond the Labour party - including from the Liberals Keynes and Beveridge. The same is true of much of Blair's programme: Scottish devolution, for example, became impossible to ignore because of the work of a coalition of churches and civic organizations as well as political parties.

Each of these examples the most lasting changes tend to happen when the top down and the bottom up come into alignment.

Seeing things this way helps to explain why some things that governments do work and others don't. It has become common to argue that governments cannot lead their societies because anything they do will backfire. So if they try to plan the economy the economy just grinds to a halt - just look at the USSR. If they try to impose family values no one takes any notice, just look at the soaring divorce rates that accompanied Margaret Thatcher and Ronald Reagan's administrations.

The economist Paul Ormerod published a book this year which made a sophisticated variant of the claim that everything fails, from town planning, to racial harmony.

But the examples of failure are usually ones where governments tried to impose change against the grain - when they tried too hard to lead society rather than more modestly following it. Where they have gone with the grain governments have been remarkably successful. A couple of years ago when preparing a stocktake for the Cabinet I looked back at the work done by Ted Heath's think-tank, the CPRS in the early 70s and although some of the issues were just the same - Rhodesia then, Zimbabwe now, joining the Common Market then, joining the Euro now - a surprising proportion of the things that most troubled civil servants and ministers then - from strikes to chronic old age poverty - had largely gone away.

When you studied the biggest advances - like growing numbers in universities or rising life expectancy - it became clear how much these had depended on many changes working to reinforce each other: in the case of health new drugs and surgical procedures, but also new eating habits, a growing interest in fitness, and the demands of a more knowledgeable public and thousands of self help groups.

I think that the best governments understand this and make themselves open, resisting the optical illusion that all change emanates from their unique wisdom.

The media often presents the Blair administration as government by cabal and it's true that many important discussions take place on the sofa in his office. But his government has also been remarkably open; much more of the business of government has been made visible - from interest rate decisions to food regulations - and there has been much more use of outsiders, of task forces - like Adair Turners pensions commission that will report later this year, seminars held at No 10, laws published in draft.

Half the staff of the Strategy Unit for example, which I was responsible for, came from outside government and much of its work in progress was published on the web. More than a few voluntary organisations have complained that the one thing nearly as bad as never being consulted is being consulted all the time.

But new Labour in power has often been ambiguous about its willingness to be open, and about its willingness to share power and devolve. One of Michael Young's consistent themes was that too big a state, however well intentioned, would sap people's initiative and their moral capacity and 8 years into new Labour's time in power its legacy in this respect remains unclear. Will it be seen to have spread power more widely? Will it have made people feel more in control of their own lives? Or will it end up having been another government that did things to people, and so left them resentful even of the things that worked?

I mentioned earlier that there have only been three truly transformative administrations over the last century, in 1906, 1945 and 1979.

But there was also something else that made them radical and this I think goes to the heart of the issue. All three consciously changed the balance of power, and left large parts of the population feeling more in control of their own lives than they had been before.

A very old Chinese saying states that when a true leaders work is done the people say 'we did it ourselves'. That probably remains the best way to think of political leadership. The best leaders are not the ones on a white charger heading off towards enemy lines. But the ones who find a way of unlocking the powers we already have.